This error occurs on several of our devices after flashing new firmware. This new firmware is build using SDK6.We have seen this issue before. Probably caused by flashing big binaries and intentionally overwriting flash variables.

Previous we flashed 'td1204_modem_SOFT1450.bin' and the problem resolved. Unfortunately this magic does not happen using 'td1204_modem_SOFT2065.bin'. Flashing 2065-version will lead to the 'invalid key' error.

At this moment we have 3 module (all td1204) running the same binary of our own firmware. Two of them have invalid key errors, one is doing fine ( evb1204 ). They all run perfectly using td1204_modem_SOFT1450.

Does anyone know a procedure to retrieve or restore these magical key data?